SURFACTANT-ENHANCED ULTRAFILTRATION OF HEAVY-METALS FROM WASTE STREAMS WITH PILOT-SCALE SYSTEM

A semi-automatic pilot-scale membrane system was utilized to perform m etal separations from simulated and real industrial wastewaters. Five heavy metals (cadmium, lead, copper, nickel, and zinc) in a simulated wastewater, alone and together, were substantially removed by surfacta nt-enhanced ultrafiltration using deoxycholic acid, a derivative of ch olesterol. The underlying principle is to increase the size of target metal ions by fixing them to larger surfactant macromolecules so they can be retained by a compatible membrane. This research showed that tr ansmembrane pressure had a minimal effect on metal removal whereas the surfactant-to-metal ratio had substantial influence. Selective and to tal removal of metal ions has been achieved by applying an appropriate level of surfactant-to-metal (S/M) ratio. The optimal S/M ratio for e ffective metal removal (99.9+ rejection ratio) is around 2.5 for deoxy cholic acid. Deoxycholic acid also showed the capacity to selectively remove metal cations (lead, copper, nickel, zinc and iron) from metal anions (chromate), which can be further reused in metal finishing plan ts.